Field of the Invention
The invention relates to endless belts for conveyors and, more particularly, to an endless belt having at least one sidewall.
Description of the Related Art
The use of thermoplastic belts in conveyors is known. Generally they are of two general configurations: flat or toothed. Flat belts are generally friction driven, and toothed belts are driven by pulleys or sprockets.
Particularly in the food industry, it is known to add sidewalls to a flat belt. Sidewalls are typically walls that extend normally relative to the belt surface to assist in retaining loads on the belt. Usually there are two walls extending longitudinally on the belt spaced from each other, so that loads can be accommodated between them. To accommodate wrapping the belt over a pulley or a nose bar, the sidewalls are either slotted or corrugated. An exemplary prior art belt 1 with a corrugated sidewall is illustrated in FIG. 1 where a body portion 2 of the belt is wrapping a pulley 4. The body portion comprises a load surface 6 and a drive surface 7. Sidewalls 8 extend from the load surface 6 and are corrugated, meaning that each is folded and shaped in an accordion-like fashion. When the body portion 2 wraps or bends around a portion of the pulley 4 in a conventional manner to be driven by frictional engagement of the pulley 4 and the drive surface 7, an upper portion of the corrugated sidewall 8 unfolds to accommodate the bend.
Limitations and problems exist in known belts with corrugated sidewalls. For example, a reverse bend, where the load surface wraps or bends around a pulley, is difficult to accommodate to a small radius with corrugated sidewalls because the height of the sidewalls tends to influence the radius of a reverse bend. The higher the sidewalls, the larger the radius that is required in order to effectively wrap a pulley. Another problem with corrugated sidewalls is that they are hard to clean because the contents on the conveyor belt may become trapped within the folds. Also, the tops of the folds tend to wear more in reverse bends, especially with smaller bend radius. As well, some effectiveness is lost in scraping a belt because the scraper must accommodate the folds and motion of corrugated sidewalls. Further, corrugated sidewalls tend to have a larger footprint on the surface of the belt, thereby requiring a wider belt to accommodate the load. They add significant weight to the belt making it difficult to handle and requiring more energy to operate.
An exemplary prior art belt 10 with a non-corrugated sidewall is illustrated in FIGS. 2 and 3 comprising a body portion 11, a load surface 12, and a drive surface 14. Sidewalls 30 extend from the load surface 12 and comprise a number of slots 32, spaced from each other at regular intervals. Each slot 32 extends from a top edge 33 of the sidewall 30 to a point 34 just above the junction of the sidewall with the load surface 12. When the body portion 11 wraps or bends around a portion of the pulley 40 in a conventional manner to be driven by frictional engagement of the pulley 40 and the drive surface 14, as show in FIG. 3, an upper portion of the sidewall 30 separates at the slots 32 to facilitate the bend. In this configuration, a span of the body portion 11 between the pulleys 40 will carry loads on the load surface 12 as the endless belt 10 travels in the direction indicated by arrow 46. The slots 32 in the sidewalls 30 enable the sidewalls to remain generally normal relative to the load surface 12 as the body portion 11 wraps or bends around a pulley 40.
But limitations and problems also exist in known belts with non-corrugated sidewalls. For example, the edges of the upper portion of the sidewall adjacent to each slot tend to butt each other, instead of sliding past each other in a reverse bend. Also, the “root” of the slot (34) is susceptible to “crack propagation” if not designed properly due to the opening and closing motion of the slots 32 during a bend. The angle of the slot 32 does not promote “self-cleaning” and will harbor food stuffs, since the slot 32 is cut normal to the sidewall, i.e.: at an angle of 90 degrees.